The fundamental steps of processing color light-sensitive materials generally include a color developing step and a desilvering step. Thus, an exposed color light-sensitive material is subjected to a color developing step, where silver halide is reduced with a color developing agent to produce silver and the oxidation product of color developing agent, which in turn reacts with a color former to yield a dye image. Subsequently, the color light-sensitive material is introduced into a desilvering step, where silver produced in the preceding step is oxidized with an oxidizing agent (usually called a bleaching agent), and dissolved away with a silver ion complexing agent (usually called a fixing agent). Therefore, only a dye image remains in the thus processed color light-sensitive material. In addition to the above-described two fundamental steps of color development and desilveration, actual development processing generally involves auxiliary steps for maintaining the photographic and physical quality of the resulting image, and for improving the preservability of the image. For example, a hardening bath may be used for preventing a light-sensitive layer from being excessively softened during color photographic processing, a stopping bath may be used for effectively stopping the developing reaction, an image stabilizing bath may be used for stabilizing the image, and a layer removing may be used for removing a backing layer on the support.
The above-described desilvering step may be conducted in two ways: one way uses two steps employing a bleaching bath and a fixing bath; and the other way is more simple and is conducted in one step employing a bleach-fixing bath containing both a bleaching agent and a fixing agent for the purpose of accelerating the processing and reducing the labor required.
Ferricyanide and ferric chloride, heretofore used as bleaching agents, are good bleaching agents because they have high oxidizing power. However, a bleaching solution or bleach-fixing solution containing ferricyanide as a bleaching agent releases poisonous cyanide by photolysis causing environmental pollution. Accordingly, waste processing solutions thereof must be rendered harmless from the viewpoint of environmental pollution. A bleaching solution containing ferric chloride as a bleaching agent is not desirable because materials of vessels in which the solution is filled up are liable to be corroded due to the extremely low pH and high oxidizing power of the solution. In addition, iron hydroxide is precipitated in an emulsion layer during a water washing step after a bleaching step using ferric chloride, thereby resulting in staining.
On the other hand, potassium dichromate, quinones, copper salts, etc., which have been used as bleaching agents have weak oxidizing power and are difficult to handle.
In recent years, bleach processing using a ferric ion complex salt (e.g., aminopolycarboxylic acid-ferric ion complex salt, particularly iron (III) ethylenediaminetetraacetate complex salt, etc.) as a major bleaching bath component has mainly been employed in processing color light-sensitive materials in view of the acceleration and simplification of the bleaching provided and the need to prevent environmental pollution.
However, ferric ion complex salts have a comparatively low oxidizing power, and therefore, often have insufficient bleaching power. A bleaching or bleach-fixing solution containing such a complex salt when bleaching or bleach-fixing a low speed color light-sensitive material containing, for example, a silver chlorobromide emulsion as a major component. However, insufficient desilveration occurs in such a solution due to insufficient bleaching power or requires a long time to bleach when processing a high speed, spectrally sensitized color light-sensitive material containing a silver chlorobromoiodide emulsion or a silver iodobromide emulsion as a major component, particularly color reversal light-sensitive materials for photographing or color negative light-sensitive materials for photographing comprising an emulsion containing a larger amount of silver.
Known bleaching agents other than ferric ion complex salts include persulfates. Persulfates are usually used in a bleaching solution together with a chloride. However, persulfate-containing bleaching solution has less bleaching ability than ferric ion complex salts, and thus, requires a substantially long period of time for bleaching.
In the color light-sensitive materials, sensitizing dyes are generally employed for the purpose of spectral sensitization. In particular, when a tabular grain silver halide emulsion containing a large amount of silver or having a high aspect ratio in order to achieve high sensitivity is employed, a problem occurs in that sensitizing dyes adsorbed on the surfaces of silver halide grains interfere with the bleaching of silver formed in the development of the silver halide.
Heretofore, various compounds have been proposed as means for enhancing the bleaching ability of color light-sensitive materials by incorporating such as a bleach accelerating agent therein.
Examples of such bleach accelerating agents include mercapto compounds as described in U.S. Pat. Nos. 3,893,858 and 4,508,816, Japanese Patent Application (OPI) Nos. 147529/78, 58532/77 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), etc., or compounds having an ##STR2## group as described in U.S. Pat. No. 4,481,290, etc. However, these compounds do not always show a satisfactory bleach accelerating effect. Moreover, many of them have a disadvantage in that they cause insufficient fixing. Further, diamino compounds as described in U.S. Pat. No. 4,552,834 often have a less bleach accelerating effect than desired effect, although usually being sufficient for practical purpose of fixing.